Multipoint switch



May 2, 1961 Filed April 30, 1959 J. W. FORREST MULTIPOINT SWITCH 3Sheets-Sheet 1 REDUCTION May 2, 1961 J. w. FORREST MULTIPOINT SWITCHFiled April 30, 1959 3 Sheets-Sheet 2 dew/away;

MN MA N-j y 1 J. w. FORREST 2,982,824

MULTIPOINT SWITCH Filed April 50, 1959 3 Sheets-Sheet 3 United Statesatent Office 2,982,824 Patented May 2, 1961 MULTIPOINT SWITCH John W.Forrest, West Acton, Mass, assignor to Technology Instrument Corporationof Acton, a corporation of Massachusetts Filed Apr. 30, 1959, Ser. No.810,085

3 Claims. (Cl. 200-24) This invention relates to multiple-point rotaryelectrical switch assemblies.

A common requirement in the electrical and electronics industries is toprovide switching devices which will permit simultaneous and variableselection of single signals from two groups of signals whereby theselected signals may be combined electrically or functionally tocontrol, modify, initiate, or terminate operation of suitable devices,as, for example, a gate circuit. Conventionally, this is achieved byproviding a switch assembly having a plurality of switch positions equalin number to the total number of possible combinations of signals witheach position having a plurality of contact terminals equal in number tothe number of groups of signals from which signals are to be selected.Obviously, the greater the number of combinations of signals, the morecomplex and expensive will be the switch assembly. Moreover, it will bemore difficult to wire and check.

Accordingly, the primary object of this invention is to provide amultiple-point rotary electric switch assembly which is compact,economical, easy to manufacture, and easy to wire.

A more specific object of this invention is to provide an electricswitch assembly capable of a relatively large number of switchingcombinations and which comprises a conventional multipoint switchcoupled to a segmented commutator switch through a reverted gear train.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the invention becomes better understoodby reference to the following detailed description when considered inconnection with the accompanying drawings, wherein:

Fig. l is a schematic representation of the switch assembly of thepresent invention;

Fig. 2 is a side elevation, partly in section, of the switch assembly;

Fig. 3 is a sectional view taken along line 3-3 of Fig. 2;

Fig. 4 is a plan view, partly in section, of the same switch assembly;

Fig. 5 is a front end view of the dial section of the switch assembly;

Fig. 6 is a view taken from the standpoint of line 6-6 in Fig. 2;

Fig. 7 is a rear view of a second form of contact assembly for thecommutator switch;

Fig. 8 is a front view of the same contact assembly;

Fig. 9 is a side view in elevation of the same contact assembly;

Fig. 10 is a rear view of the hub element of the same contact assembly;and

Fig. 11 is a sectional view taken along line 1111 of Fig. 10.

The embodiment of the invention selected for description andillustration provides 40 discrete switching combinations with only 15wiring connections. As illustrated schematically in Fig. 1, the selectedembodiment of the invention comprises a S-segment commutator switch S1,a conventional 8-position rotary switch S2, and a reverted gear train Gcoupling switches S1 and S2 which causes the wiper arm of switch S1 torotate at /5 the speed of rotation of the contact arm of switch S2. Onecomplete turn of the contact arm of switch S2 rotates the wiper arm ofswitch S1 through only one of the five segments, giving eight discreteswitch positions. Five turns of switch S2 rotates the wiper arm ofswitch S1 through all five segments, giving forty discrete positions.Thus, if two groups of signalsone consisting of five different signalsand the other consisting of eight different signalsare applied to thesegments of switch S1 and the contacts of switch S2 respectively,operation of the switches will yield forty different signal combinationsas outputs, each signal combination consisting of one signal for switchS1 and one signal for switch S2. Yet, the total number ofelectricalconnections required to be made to switches S1 and S2 is only 15. Aconventional switch assembly would require many more electricalconnections to provide the same number of signal combinations.

Turning now to Figs. 2-5, switch S1 comprises a commutator plate 10preferably formed of a phenolic resin and provided on one side withprinted circuit elements comprising a plurality of arcuate conductivesegments, A, B, C, D, and E, forming a concentric circle about an innercontinuous conductive ring or band F. The circuit elements are flushwith the surface of plate 10 and are composed of silver plated overcopper. If desired, the silver may be replaced by a plating of rhodiumapplied over a bright nickel coating on copper.

The spacing between the adjacent ends of the arcuate segments should bekept as small as possible. A spacing of $4 of an inch has been found tobe satisfactory. The arcuate segments A-E each have a tab 12. These tabsare conductively connected to separate terminals 14 secured to theopposite side of plate 10. Band F has a similar tab 16 conductivelyconnected to another terminal (not shown) secured on the rear side ofplate 10.

Extending through an opening in plate 10 located centrally of conductiveband F is a first rotatable hollow shaft 17 inside of which is rotatablydisposed a second solid shaft 18. Secured to shaft 17 in spaced relationto plate 10 is a split collar 20 which carries an angular conductivemember comprising two substantially radially extending arms 24 and 26formed integral with a connecting portion 28. The latter portion issecured to collar 20. The free ends of arms 24 and 26 are bent back andprovided with contact points 30 and 32 respectively. Contact 30 engagesthe arcuate segments A-E and contact 32 engages conductive ring F.

As seen in Fig. 4, plate 10 and three additional plates 34, 36, and 37are held in spaced alignment with each other by conventional standoffscomprising two long screwbolts 38, nuts 40, and cylindrical spacers 42,44, and 46. The foremost plate 34 is provided with tapped bosses 48 toreceive screws 50 which are used to attach the entire switch assembly toa suitable plate or chassis walle.g., plate 52. Shafts 17 and 18 aremade long enough to project through a suitable opening in the plate onwhich the switch assembly is mounted. Mounted on outer shaft 17 is adial 54 and mounted on inner shaft 18 is a solid knob 56. Dial 54 has 40equally spaced graduations 58. An indicator 60 having a single line 62engraved therein is provided to facilitate reading the setting of dial54. Indicator 60 is attached by screws 64 to the plate 52 which supportsthe assembly.

An additional plate 66 is located between plates 10 and 36. Plate 66 issupported from plate 36 by means of a pair of spacers 68 and screws 70which are screwed into tapped openings provided in the opposite ends ofthe spacers. Seated in an openingin plate 66 is a bearing sleeve 72through which extends shafts 17 and 18. One end of bearing 72 abutsplate 10. The opposite end hasa flange=74 whichis held inengagementwith'plate 66 by an O-ring 76 mountedon shaft.17:. Shaft.-17.t'ermi:-':.

nates at a point; intermediate platesi66 and 36." A rela-r tively largegear-.StlLis mounted'on the end of shaft 17.

Just beyond gear 80, shaft 18 is enlarged to the same diameter asshaft17. This enlarged portion of shaft 18 I is designated 18a in thedrawings and extends through.

and beyond 'plate' 36 and is connected to a removable coupling 32.Mounted on shaft portion 18a is a secondv smaller gear 84.

An idlershaft '88 has its opposite ends supported in. suitable openingsin plates .36 and 66. Two O-rings 90' Gear 96 meshes with gear 84 onshaft 18. Thus when shaft 18 is rotated by means of knob 56, gear 84will drive gear 96, gear 96 will drive idler shaft 88, shaft 88 willdrive gear 94, gear'94 will drive gear 80, and gear 80 will drive shaft17 to turn dial 54. In the illustrated embodiment, the four gears aresized to provide a :1 speed'ratio between inner shaft 18 and outer shaft17, whereby when shaft 18 is rotated five times, coupling 82 will makethe same number of revolutions while shaft 17 and contact member 24 anddial 54 will make a single complete revolution. Dial 54 provides anindication of the degree of rotation of both shafts.

Switch S2 may be of any conventional construction; and as illustrated,it is constructed according to the teachings of US. Patent No.2,012,492.

As seen in Figs. 2 and 6, switch S2 comprises two plates 100 and 102held together by two standoffs designated generally by numeral 104.Secured to plate 100 is a bushing 106 which surrounds and supports arotatable operating shaft 108. Bushing 106 extends through a hole inplate 37 and is attached thereto by means of a nut 110. The end ofoperating shaft 108 is coupled directly to shaft 18 by means of coupling82. Hence, shafts 18 and 108 rotate at the same speed.

Plate 100 has a plurality of struck up portions 112 symmetricallydisposed in a circle around shaft 108 which extends through centralopenings in plates 109 and 102. A spring member 114 doubled back uponitself is mounted on shaft 108. Spring member 114 is locked to shaft 108by a pair of wings 116 provided on the shaft. The outer or free end ofspring member 114 is provided with an aperture which is adapted tomaintain a ball bearing 118 in frictional engagement with plate 100.When shaft 108 is turned, spring member-114 will yield to permit ballbearing 118 to ride 'over the struck up portions 112; and when the forceturning shaft 103 is removed, the ball will automatically seat itselfbetween two of the struck up portions.

Plate 102 is made of non-conductive material and riveted to it are eightcontact members 120 arranged symmetrically in a circle. A ninth contactmember 122 ditfering in length is disposed between two contact members120. Attached to shaft 108 is a rotor 124 which carries a conductivering 126 provided with a radial tab 128. "Contact members 120 terminateshort of ring 126' but are long enough'to be contacted in turn by tab128 as shaft 108'is rotated. The ninth contact member 122' is longerthan contact members 120 and is in frictional contact with ring 120constantly. Contact members 120 are disposed so that tab 128 will makecontact therewith only when ball bearing 118 is located between two ofthe struck up portions 112. At their-outer ends, contacts 120 and 122arebent back to form terminal lugs 132 "provided with suitable openings134 into which.

connecting" leads may be soldered. Signals are applied to contacts 120and picked ofi by contact 122.

It is to'be noted that switch S2 may be modified by adding one or ,morenon-conductive plates like plate 102 and a corresponding number ofrotors like rotor 124 so as to increase the number of signals that maybe switched by switch S2 without at the same time increasing the numberof switching combinations. The latter is determined by the number ofconductive segments in switch S1, the number of terminals in switch S2,and the speed ration provided by the reverted gear train G.

Figs. 7-11 shows an alternative form of contact assernblyforithescommutator swith S1. It may be substituted in place of thecontact assembly comprising elements 2032.

' The alternative form comprises a circular insulator disc provided witha central opening '142 and a hub 144 having a reduced diameter extension146 which fits into opening 142. Screws 148 lock the hub to disc 140.Screws 148 extend through openings in disc 140 and are secured in tappedopenings 150 in the hub 144. Hub 144 has a central opening 152 toreceive shaft 17 and a pair of radially extending tapped holes 154 forreceiving set screws for locking the hub to shaft 17.

Mounted on the rear side of disc 140 are two identical contact leafs 158and 160. -Leafs 158 and 160 are of arcuate shape and are bent adjacenttheir ends as at 162 and also intermediate their ends as at 164 so thattheir midpoints and their ends lie in different planes. At theirmidpoints, leafs 158 and 160 are provided with rounded contacts 168 and170 respectively. The ends of contact leaf 158 are secured to disc 140along a line corresponding to a first chord of a circle defined by theperiphery of the disc. Contact leaf 160 is secured to disc 140 along aline corresponding to a second chord spaced a shorter distancefrom thecenter of the disc. When hub 144 is mounted on shaft. 17 adjacentcommutator plate 10, contact 168 will engage conductive ring F andcontact 170 will engage .thearcuate segments A-E.

Contact leafs 158 and160 are secured to the disc 140 by means of metaleyelets174 and 176 respectively and are conductively connected to eachother by bus wires 178 whose ends are soldered in the eyelets.

The contact assembly of Figs. 71l has a greater life The arms- 24 and 26are supported at only one end; and, therefore,

than the contact assembly shownin Fig. 3.

they tend to twist about connecting portion 28 when shaft 17 is rotated.This torsional stress is avoided in the contact assembly of Fig. 7 sinceboth ends ofthe two contact leafs are anchored and the contacts 168 and170 are located between theanchored ends.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. .It is to beunderstood, therefore, that the invention is not limited in itsapplication to the details of and a contact arm connected to said secondshaft and disposed to engage each fixed'contact in turn as said secondshaft is rotated, means connecting said first andsecond shafts fordriving said first shaft from said second shaft at a speed equal to 1/ttimes the speed of said second shaft when said second shaft is rotated,acircular dial mounted on said first shaft having n times t graduationsinscribed thereon, n and t both being whole num-. bers, and meanscooperating with the graduationson said dial to indicate the relativepositions of said wiper arm and said contact arm. 1

2. A rotary switch comprising a commutator plate having a plurality ofarcuate-shaped contact segments on one face thereof, said contactsegments arranged end to end in a circle With the adjacent ends ofsuccessive segments in close-spaced relation with each other, a likeplurality of terminals each connected to one of said segments, saidplate also having a continuous contact band on said same face in coaxialrelation with said circle of contact segments, a terminal connected tosaid contact band, first and second contact elements each of arcuateshape and constructed of flat, resilient, conductive material, arotatable member constructed of insulating material, means securing bothends of said contact elements to said rotatable member with themidpoints of said first and second contact elements located at differentdistances from the center of said rotatable member, said contactelements bent away from said rotatable member so as to be spacedtherefrom at their midpoints, said rotatable member located so that saidfirst contact element slidably engages one of said contact segments andsaid second contact element slidably engages said contact band, meanselectrically connecting said first and second contact elements, andmeans for rotating said rotatable member whereby to advance said firstcontact element along successive segments while said second contactelement is advanced along said contact band.

3. A rotary switch as defined by claim 2 wherein the ends of said firstand second contact elements are secured to one side of said rotatablemember by means of conductive eyelets, and further wherein said meanselectrically connecting said'first and second contact elements are wireswhose ends are soldered in said eyelets.

References Cited in the file of this patent UNITED STATES PATENTS2,700,076 Goode Jan. 18, 1955 2,832,854 Doyle et a1 Apr. 29, 19582,852,628 Fry Sept. 16, 1958

